Dynamically calibrated pre-distortion

ABSTRACT

Systems and methods are provided for adaptive control of pre-distortion during signal transmissions. While applying pre-distortion during processing of an input signal for transmission, feedback data may be generated based on a plurality of feedback signals, and adjustments to the pre-distortion may be applied to the pre-distortion based on the feedback data. Each of feedback signals corresponds to a particular processing stage performed during the processing of the input signal. Generating the feedback data comprises applying adjustments to the plurality of feedback signals based on a type and/or a source of at least one feedback signal, with the adjustments comprising one or more of: applying a gain to one of the plurality of feedback signals; applying a delay to one of the plurality of feedback signals; and modifying a first one of the plurality of feedback signals based on a second one of the plurality of feedback signals.

CLAIM OF PRIORITY

This patent application is a continuation of U.S. patent applicationSer. No. 14/595,896, filed Jan. 13, 2015, which makes reference to,claims priority to and claims benefit from the U.S. Provisional PatentApplication Ser. No. 61/926,428, filed Jan. 13, 2014. Each of the aboveidentified applications is hereby incorporated herein by reference inits entirety.

TECHNICAL FIELD

Aspects of the present disclosure relate to communication systems andtechnologies. More specifically, certain implementations of the presentdisclosure relate to methods and systems for dynamically calibratedpre-distortion.

BACKGROUND

Conventional systems and methods for pre-distortion can be inefficientand ineffective. Further limitations and disadvantages of conventionaland traditional approaches will become apparent to one of skill in theart, through comparison of such systems with some aspects of the presentdisclosure as set forth in the remainder of the present application withreference to the drawings.

BRIEF SUMMARY

System and methods are provided for dynamically calibratedpre-distortion, substantially as shown in and/or described in connectionwith at least one of the figures, as set forth more completely in theclaims.

These and other advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts an example transmitter that may be operable to performdynamic calibration of pre-distortion, in accordance with the presentdisclosure.

FIG. 2A depicts an example implementation of a feedback conditioningcircuit, in accordance with the present disclosure.

FIG. 2B depicts another example implementation of a feedbackconditioning circuit, in accordance with the present disclosure.

FIG. 3 depicts a flowchart of an example process for dynamic calibrationof pre-distortion during signal transmission, in accordance with thepresent disclosure.

FIG. 4 depicts a flowchart of an example process for controllingpre-distortion adjustments, based on feedback conditioning, in a systemduring dynamic calibration of pre-distortion applied in signaltransmission, in accordance with the present disclosure.

FIG. 5 depicts another example transmitter that may be operable toperform dynamic calibration of pre-distortion, where the pre-distortionis implemented in the analog side, in accordance with the presentdisclosure.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (e.g., hardware), and any software and/orfirmware (“code”) that may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory (e.g., a volatileor non-volatile memory device, a general computer-readable medium, etc.)may comprise a first “circuit” when executing a first one or more linesof code and may comprise a second “circuit” when executing a second oneor more lines of code. Additionally, a circuit may comprise analogand/or digital circuitry. Such circuitry may, for example, operate onanalog and/or digital signals. It should be understood that a circuitmay be in a single device or chip, on a single motherboard, in a singlechassis, in a plurality of enclosures at a single geographical location,in a plurality of enclosures distributed over a plurality ofgeographical locations, etc. Similarly, the term “module” may, forexample, refer to a physical electronic components (e.g., hardware) andany software and/or firmware (“code”) that may configure the hardware,be executed by the hardware, and or otherwise be associated with thehardware.

As utilized herein, circuitry or module is “operable” to perform afunction whenever the circuitry or module comprises the necessaryhardware and code (if any is necessary) to perform the function,regardless of whether performance of the function is disabled or notenabled (e.g., by a user-configurable setting, factory trim, etc.).

As utilized herein, “and/or” means any one or more of the items in thelist joined by “and/or”. As an example, “x and/or y” means any elementof the three-element set {(x), (y), (x, y)}. In other words, “x and/ory” means “one or both of x and y.” As another example, “x, y, and/or z”means any element of the seven-element set {(x), (y), (z), (x, y), (x,z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one ormore of x, y, and z.” As utilized herein, the term “exemplary” meansserving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “for example” and “e.g.” set off lists of oneor more non-limiting examples, instances, or illustrations.

FIG. 1 depicts an example transmitter that may be operable to performdynamic calibration of pre-distortion, in accordance with the presentdisclosure. Shown in FIG. 1 is an example transmitter 100.

The transmitter 100 may comprise suitable circuitry for processing andtransmitting signals, which may be configured for communication inaccordance with one or more wireless or wire-based interfaces (and/orprotocols). The transmitter 100 may be configured to perform dynamiccalibration of pre-distortion during transmission related operations.For example, as shown in the example implementation depicted in FIG. 1,the transmitter 100 may comprise an upsampling circuit 102, apre-distortion circuit 104, an upsampling circuit 106, adigital-to-analog convertor (DAC) circuit 108, a programmable gain poweramplifier (PGPA) circuit 110, a feedback conditioning circuit 112, and apre-distortion control circuit 114. Also shown is a sensor 120, whichmay be a temperature (“temp”) sensor. The sensor 120 may be part (e.g.,a component) of the transmitter 100. Alternatively, in some exampleimplementations, the sensor 120 may be separate from (butcommunicatively coupled to) the transmitter 100.

Each of the upsampling circuits 102 and 106 may be operable to generatean output signal by upsampling an input signal.

The pre-distortion circuit 104 may be operable to modify (e.g., distort)characteristics (e.g., phase, frequency, and/or amplitude) of an inputsignal, such as based on a control signal (and/or pre-programmedsettings).

The DAC circuit 108 is operable to convert a digital input signal into acorresponding analog representation (output). The DAC circuit 108 may beconfigured to operate with any suitable digital-to-analog conversiontechnique or scheme.

The PGPA circuit 110 may be operable to generate an output signal byamplifying an input signal. The PGPA circuit 110 may be configured toamplify the input signal based on particular criteria—e.g., so that theoutput signal would have sufficient power for propagation over aphysical medium to a receiver. Further, the PGPA circuit 110 may beconfigured to introduce certain modification—e.g., phase, frequency,and/or amplitude distortion. In some implementations, the PGPA circuit110 may be implemented and/or configured to have frequency dependent andfrequency independent amplitude and/or phase response.

The pre-distortion control circuit 114 may be operable to control thepre-distortion circuit 104, such as by generating a control signal(e.g., signal 115 in FIG. 1) that may control or adjust thepre-distortion circuit 104, or operations thereof. For example,pre-distortion control circuit 114 may be operable to adjust, via thecontrol signal 115, tap coefficients of one or more filters of thepre-distortion circuit 104. The pre-distortion control circuit 114 mayreceive as an input a control signal (control signal 113 in FIG. 1), andmay generate its own control signal 115 based on that input controlsignal. Example implementations of the feedback conditioning circuit 112are described below with reference to FIGS. 2A and 2B.

The feedback conditioning circuit 112 may be operable to control thepre-distortion control circuit 114, such as by generating the controlsignal 113. In particular, the feedback conditioning circuit 112 isconfigured to operate in feedback manner, such as by conditioning one ormore signals obtained further down (relative to the pre-distortioncircuit 104) the transmit path for use in the pre-distortion circuit114. For example, as shown in FIG. 1, feedback conditioning circuit 112may condition one or more of: output signal of the pre-distortioncircuit 104 (e.g., signal 105 in FIG. 1), output signal of theupsampling circuit 106 (e.g., signal 107 in FIG. 1), output signal ofthe DAC circuit 108 (e.g., signal 109 in FIG. 1), and output signal ofthe PGPA circuit 110 (e.g., signal 111 in FIG. 1), to make the signal(s)suitable for use by the pre-distortion circuit 114. The outcome of suchconditioning is reflected in the control signal 113.

The sensor 120 comprise suitable circuitry (and/or other hardware) forobtaining particular sensory information (e.g., temperature), and forgenerating a corresponding control signal (e.g., signal 121 in FIG. 1)indicating or reporting that sensory information. For example, thesensor 120 may be operable to sense and indicate (via the control signal121) a temperature of the transmitter 100 generally and/or of one ormore of the components 102, 104, 106, 108, 110 specifically.

In an example operation, starting with an input signal 101 (e.g., abaseband data-carrying signal), the upsampling circuits 102 may upsamplethe signal 101 to generate a corresponding signal (e.g., signal 103 inFIG. 1). The signal 103 may then be input into the pre-distortioncircuit 104, which may modify (i.e., distort) characteristics (e.g.,phase, frequency, and/or amplitude) of the signal 103, such as based onthe control signal 115, to generate a pre-distorted signal (e.g., signal105 in FIG. 1). The pre-distorted signal 105 may be input into theupsampling circuit 106, which may upsample the pre-distorted signal 105to generate a corresponding upsampled pre-distorted signal (e.g., signal107 in FIG. 1). The upsampled pre-distorted signal 107, which may be adigital signal, may be fed into the DAC circuit 108, fordigital-to-analog conversion thereby, resulting in corresponding analogsignal 109. The PGPA circuit 110 may then amplify the analog signal 109,to generate the corresponding signal 111, which may have sufficientpower for propagation over a physical medium to a receiver. The signal111 (or modified copy thereof) may then be transmitted, via a suitablefront-end (not shown). The PGPA circuit 110 may introduce phase,frequency, and/or amplitude distortion.

In various implementations, the transmitter 100 may be operable toperform dynamic calibration of pre-distortion, such as based onfeedback. In this regard, a goal of the modifications performed bypre-distortion circuit 104 (e.g., on the signal 103) may be to canceland/or compensate for distortion introduced by the other elementsfurther down the transmit path—e.g., the upsampling circuit 106, the DACcircuit 108, and/or the PGPA circuit 110. Such distortion maydynamically change. For example, distortion introduced by the PGPAcircuit 110 may change as certain conditions (e.g., temperature; powersupply voltage; amplitude, phase; amplitude, phase, and/or frequency ofsignal 109; etc.) may change. Accordingly, in various implementations,pre-distortion may be dynamically calibrated, such as by dynamicallyadjusting parameters of the pre-distortion circuit 104 to account forsuch changed conditions/parameters in, or near, real-time.

For example, in the particular example implementation shown in FIG. 1,the pre-distortion control circuit 114 may be used to control or adjustthe pre-distortion being performed via the pre-distortion circuit 104.The pre-distortion control circuit 114 may generate the control signal115, which may be input to the pre-distortion circuit 104 to enablecontrolling and/or adjusting operations thereof. For example, thepre-distortion circuit 104 may comprise one or more filters that areused in applying the modifications made to the signal 103, and thecontrol signal 115 may be used in, e.g., adjusting tap coefficients ofone or more filters of the pre-distortion circuit 104.

The pre-distortion control circuit 114 may be controlled based on input(e.g., the control signal 113) from the feedback conditioning circuit112 (thus facilitating the adaptive, feedback based, control ofpre-distortion). For example, the feedback conditioning circuit 112 maycondition one or more of the signal(s) 111, 109, 107, and 105; to makethe signal(s) suitable for use by the pre-distortion circuit 114. Theresult of the conditioning performed by the feedback conditioningcircuit 112 may be conveyed via the control signal 113, and ultimatelythe effect of the conditioned signals may be conveyed to (e.g., used tocontrol) pre-distortion circuit 104 via the control signal 115.

The pre-distortion control circuit 114 may also be controlled based onsensory-based input, such as from the sensor 120. For example, thesensor 120 may obtain temperature related information relating to thetransmitter 100 (and/or it various components thereof), and may outputbased thereon the signal 121, which may indicate temperature of thetransmitter 100 generally, and/or of one or more of the components 102,104, 106, 108, 110 specifically. Other factors that may be considered incontrolling the pre-distortion performed in the transmitter 100 (e.g.,being feed into and used by the pre-distortion control circuit 114) maycomprise parameters relating or pertinent to function of othercomponents (e.g., PGPA circuit gain).

In an example implementation, adjusting operation of the pre-distortioncircuit 114 (e.g., by changing and/or updating pertinent operationalparameters of the pre-distortion circuit 114, such as filter taps) maybe periodic, event-based, and/or conditional. For example, thepre-distortion circuit 114 (or operation thereof) may be updated oradjusted periodically, such as every N (a positive real number) seconds,and/or in response to a particular event, such as transmission of everyM^(th) packet (a positive real number). Conditions which may determinewhether and/or when the pre-distortion circuit 114 (or operationthereof) is updated or adjusted may comprise, for example, absolutecharacteristics (e.g., phase, frequency, power, etc.) of one or morereference signals (e.g., signal 109 and/or signal 111), relativecharacteristics (e.g., phase, frequency, power, etc.) of one or morereference signals (e.g., signal 109 and/or signal 111), parametersrelating or pertinent to function of other components (e.g., PGPAcircuit gain), absolute environmental condition (e.g., only update whentemperature is outside a predetermined window), and relativeenvironmental condition (e.g., only update when temperature has changedby more than X (a real number) degrees relative to the temperature atthe time of the last update).

In this regard, an absolute characteristic condition may be determinedbased on state (e.g., value) of a particular characteristic (e.g.,phase, frequency, power) of a reference signal in comparison to one ormore applicable thresholds or criterion, regardless of a previous stateof that characteristic. For example, an update or adjustment may beconditionally performed only when power of the signal 109 is above (orbelow) a particular threshold, when frequency of the signal 111 is above(or below) a particular threshold, etc. A relative characteristiccondition may be determined based on measure (e.g., amount) of change ina particular characteristic (e.g., phase, frequency, power) of areference signal in relation to a previous state of that characteristic,particularly the measure of change in comparison to one or moreapplicable thresholds or criterion. For example, an update or adjustmentmay be conditionally performed only when phase of the signal 109 haschanged (increased or decreased) by more than a predetermine amountrelative to the phase at the time of the last update, when power of thesignal 111 has changed (increased or decreased) by more than adetermined amount relative to the power at the time of the last update.

The conditions (particular reference signal and/or particularcharacteristic thereof, particular parameter relating particularcomponent, particular environment condition, etc.), type of condition(e.g., absolute vs. relative), and/or applicable parameters (e.g.,thresholds, windows, etc.) or criteria used in determining and/orassessing when conditions (relative or absolute) are met may beper-determined or pre-programmed. Further, the conditions, conditiontypes, and/or applicable parameters (e.g., thresholds, windows, etc.) orcriteria may be modifiable—e.g., based on user input.

In an example implementation, to further enhance performance (e.g.,power consumption), the pre-distortion control circuit 114 and/or thefeedback conditioning circuit 112 may be fully or partially powered downbetween updates of parameters of the pre-distortion circuit 104.

In an example implementation, to further enhance performance of thetransmitter 100, particularly with respect to the pre-distortionperformed by it and/or the dynamical calibration of such pre-distortion,equalization may be used. For example, linear distortion of the PGPAcircuit 110 may be equalized before use in controlling pre-distortion(e.g., before use in estimating pre-distortion nonlinear parameter(s)).With reference to the implementation shown in FIG. 1, the output signalof the PGPA circuit 110 (e.g., signal 111, tapped as feedback input),may be equalized (e.g., in the feedback conditioning circuit 112) beforebeing considering PGPA linear distortion during the feedbackconditioning stage.

In some instances, there may be variations in performance and/orcapabilities between component(s) in the transmit path and component(s)used in the feedback/control branch, which may be accounted for whenconfiguring the feedback/control operations. For example, memory in thePGPA circuit 110 may be substantially larger than the sampling timeinterval in which pre-distortion operates, which may be accounted forduring feedback/control operations. In an example implementation, thepre-distortion may be configured to either operate at slower rate, orsome of the memory terms can be skipped which results in lowercomplexity.

In various example implementations, the feedback conditioning and/orpre-distortion control may be implemented as fully analog, fullydigital, or mixed analog-digital. For example, each of thepre-distortion control circuit 114 and the feedback conditioning circuit112 may be implemented to operate on digital and/or analog signals—thatis they would operate, when applying the functions performed thereby, onanalog or digital signals. Accordingly, these components may beimplemented to incorporate (as needed) analog-to-digital converter (ADC)circuit(s) and/or digital-to-analog converter (DAC) circuit(s), toensure that necessary conversions, to the input signal(s), the outputsignal(s), and/or intermediate signal(s) (if any), can be performed. Forexample, with reference to the implementation shown in FIG. 1, where thefeedback conditioning circuit 112 is implemented to operate on digitalsignals, the feedback conditioning circuit 112 may comprise DACcircuit(s) to apply analog-to-digital conversions to signals 109 and111. In another example implementation, where the feedback conditioningcircuit 112 is implemented to operate on analog signals whereas thepre-distortion control circuit 114 is implemented to operate on digitalsignals, the feedback conditioning circuit 112 may comprise ADCcircuit(s) to apply analog-to-digital conversions before outputtingsignal 113 (thus, this signal would be a digital signal); oralternatively the pre-distortion control circuit 114 may comprise ADCcircuit(s) to apply analog-to-digital conversions to signal 113 (whichwould be, in this case, analog signal).

In an example implementation, the pre-distortion control circuit 114and/or the feedback conditioning circuit 112 may be implemented suchthat to operate variably and/or adaptively on analog and/or digitalsignals. Thus, the pre-distortion control circuit 114 and/or thefeedback conditioning circuit 112 may be configured dynamically tooperate on analog and/or digital signals. Further, to ensure thatnecessary conversions are performed (e.g., based on the type of signalbeing input and/or being expected at the output, and/or based on thetype of operation the circuit(s) are configured to perform), thepre-distortion control circuit 114 and/or the feedback conditioningcircuit 112 may incorporate analog-to-digital converter (ADC) circuit(s)and digital-to-analog converter (DAC) circuit(s), which may beconfigured for operation as needed.

FIG. 2A depicts an example implementation of a feedback conditioningcircuit, in accordance with the present disclosure. Shown in FIG. 2A isa feedback conditioning circuit 200.

The feedback conditioning circuit 200 may be operable to controlpre-distortion control circuitry in a system. In this regard, thefeedback conditioning circuit 200 may correspond to (and thus representsan example implementation of) the feedback conditioning circuit 112 ofFIG. 1, which is used to control pre-distortion control circuit 114 ofthe transmitter 100, substantially as described with reference to FIG. 1for example. As shown in FIG. 2A, the feedback conditioning circuit 200may comprise an analog-to-digital convertor (ADC) circuit 220 and a gaincircuit 210.

The gain circuit 210 applies a gain of 1/Gp_(GPA circuit) (whereG_(PGPA circuit) is the gain of the PGPA circuit 110 of the transmitter100 described with reference to FIG. 1) to the signal 111, to generatecorresponding output signal 211, which is then digitized by ADC circuit220 for conveyance (e.g., via the control signal 113) to thepre-distortion control circuitry (e.g., the pre-distortion controlcircuit 114). The ADC circuit 220 may be implemented to further enhanceperformance. For example, the ADC circuit 220 may be a low-resolutionADC, to save power and/or space (chip area). To achieve the gain1/G_(PGPA circuit), the gain circuit 210 may use automatic gain control(AGC) techniques using a feedback loop, for example.

FIG. 2B depicts another example implementation of a feedbackconditioning circuit, in accordance with the present disclosure. Shownin FIG. 2B is a feedback conditioning circuit 250.

The feedback conditioning circuit 250 may be substantially similar tothe feedback conditioning circuit 200 of FIG. 2A, that is, it may alsobe operable to control pre-distortion control circuitry in a system. Inthis regard, the feedback conditioning circuit 250 may correspond to(and thus represent an alternative example implementation of) thefeedback conditioning circuit 112 of FIG. 1, which is used to controlpre-distortion control circuit 114 of the transmitter 100, substantiallyas described with reference to FIG. 1 for example. As shown in FIG. 2B,the feedback conditioning circuit 200 may comprise the ADC circuit 220and the gain circuit 210, as described with respect to FIG. 2A. Further,feedback conditioning circuit 250 additionally comprises a delay block260 and a combiner 270.

The feedback conditioning circuit 250 may operate in a substantiallysimilar manner to that of the feedback conditioning circuit 200, asdescribed with reference to FIG. 2A—that is by using the gain circuit210 and the ADC circuit 220 to apply and digitize gain1/G_(PGPA circuit). The additional components of feedback conditioningcircuit 250 may further allow for incorporation of a second referencesignal, particularly signal 109 (output of the DAC circuit 108 of FIG.1). In this regard, the signal 109 may be delayed by delay block 260,and then subtracted from signal 211, to generate modified output signal271 which is then digitized by ADC circuit 220 for conveyance (e.g., viathe control signal 113) to the pre-distortion control circuitry (e.g.,pre-distortion control circuit 114).

FIG. 3 depicts a flowchart of an example process for dynamic calibrationof pre-distortion during signal transmission, in accordance with thepresent disclosure. Shown in FIG. 3 is flow chart 300, comprising aplurality of example steps (represented as blocks 302-312), which may beperformed in a suitable system (e.g., transmitter 100) to facilitatedynamic calibration of pre-distortion during signal transmission.

In step 302, an original input signal may be received, being intendedfor transmission. The input signal may be a digital signal.

In step 304, initial processing may be applied to the input signal. Theinitial processing may comprise, for example, upsampling.

In step 306, pre-distortion modification may be applied (e.g., tocertain signal characteristics, such as phase, frequency, and/oramplitude) of the signal resulting from the initial processing. In thisregard, the pre-distortion modification may be configured (or adjusted)based on prior feedback (and/or current information—e.g., currenttemperature reading). Nonetheless, in some instances, the pre-distortionmodification may be initialized to allow application of suchmodification where no feedback is yet available.

In step 308, post-processing (e.g., upsampling, digital-to-analogconversion, amplification, etc.) may be applied to the signal resultingfrom application of the pre-distortion modification.

In step 310, feedback related information (e.g., information relating toor derive from intermediate signals in the transmit path and/or fromsensory data obtained in the transmitter) may be obtained.

In step 312, pre-distortion calibration related adjustments may begenerated based on the feedback information, and then applied. In thisregard, the feedback related information may be processed to determinethe adjustments. The application of the pre-distortion calibrationadjustments may be done in feedback manner; and thus it would be appliedimmediately to current operations. Thus, the pre-distortion modificationmay be adjusted during processing of the same input signal.

FIG. 4 depicts a flowchart of an example process for controllingpre-distortion adjustments, based on feedback conditioning, in a systemduring dynamic calibration of pre-distortion applied in signaltransmission, in accordance with the present disclosure. Shown in FIG. 4is flow chart 400, comprising a plurality of example steps (representedas blocks 402-412), which may be performed in a suitable system (e.g.,feedback conditioning circuit 200 or feedback conditioning circuit 250)to facilitate dynamic calibration of pre-distortion during signaltransmission.

In step 402, a first reference signal (e.g., signal 111, correspondingto output of PGPA circuit 110) may be received.

In step 404, the first reference signal may be processed. For example,gain (e.g., gain of 1/Gp_(GPA circuit)) may be applied to the firstreference signal.

In step 406, it may be determined whether additional reference signal(s)are to be used. In instances where no additional reference signal(s) areused, the process may proceed directly to step 412; otherwise (i.e., oneor more additional reference signal(s) are used, the process may proceedto step 408.

In step 408, additional reference signal(s) (e.g., signal 109,corresponding to output of DAC circuit 108) may be received andprocessed. For example, a delay (e.g., via delay block 260 in circuit250) may be applied to a second reference signal (signal 109).

In step 410, information from the additional reference signal(s) may beincorporated. For example, the second additional reference signal maybesubtracted (e.g., via combiner 270) from the output of processing thefirst reference signal.

In step 412, post-processing (e.g., analog-to-digital conversion, viaADC circuit 220) may be applied to generate a feedback conditioningbased control signal.

FIG. 5 depicts another example transmitter that may be operable toperform dynamic calibration of pre-distortion, where the pre-distortionis implemented in the analog side, in accordance with the presentdisclosure. Shown in FIG. 5 is an example transmitter 500.

The transmitter 500 may be substantially similar to the transmitter 100of FIG. 1. In this regard, the transmitter 500 may comprise suitablecircuitry for processing and transmitting signals, which may beconfigured for communication in accordance with one or more wireless orwire-based interfaces (and/or protocols), and may be particularlyconfigured to perform dynamic calibration of pre-distortion duringtransmission related operations. For example, as shown in the exampleimplementation depicted in FIG. 5, the transmitter 500 may comprise anupsampling circuit 502, a digital-to-analog convertor (DAC) circuit 504,a pre-distortion circuit 506, a programmable gain power amplifier (PGPA)circuit 508, a feedback conditioning circuit 512, and a pre-distortioncontrol circuit 514. Also shown is a sensor 510.

Each of the upsampling circuit 502, the DAC circuit 504, thepre-distortion circuit 506, the PGPA circuit 508, the sensor 510, thefeedback conditioning circuit 512, and the pre-distortion controlcircuit 514 may be substantially similar to similarly-named componentsof the transmitter 100 of FIG. 1 (i.e., the upsampling circuit 102/106,the DAC circuit 108, the pre-distortion circuit 104, the PGPA circuit110, the sensor 120, the feedback conditioning circuit 112, and thepre-distortion control circuit 114, respectively), and may be operate insubstantially similar manner.

The transmitter 500 may operate substantially in similar manner as thetransmitter 100, as described with respect to FIG. 1, for example. In anexample operation, starting with an input signal 501 (e.g., a basebanddata-carrying signal), the upsampling circuits 502 may upsample thesignal 501 to generate a corresponding signal (e.g., signal 503). Thesignal 503 may be input into the DAC circuit 504, for digital-to-analogconversion thereby, resulting in corresponding analog signal 505.

The signal 505 may then be input into the pre-distortion circuit 506,which may apply (in the analog domain) modifications (i.e., distortion)to characteristics (e.g., phase, frequency, and/or amplitude) of thesignal 505, such as based on the control signal 515, to generate apre-distorted analog signal (e.g., signal 507). The pre-distorted signal507 may be input into the PGPA circuit 508, which may amplify the analogsignal 507, to generate the corresponding amplified signal 509, whichmay have sufficient power for propagation over a physical medium to areceiver. The signal 509 (or modified copy thereof) may then betransmitted, via a suitable front-end (not shown). The PGPA circuit 508may introduce phase, frequency, and/or amplitude distortion.

The transmitter 500 may be operable to perform dynamic calibration ofpre-distortion, such as based on feedback, substantially in similarmanner as the transmitter 100, as described with respect to FIG. 1, forexample. Operation of the transmitter 500 may be modified, however, toaccount for the fact that the pre-distortion is done on the analog-side(that is after the input signal had been subject to digital-to-analogconversion, via the DAC 504). In this regard, a goal of themodifications performed by pre-distortion circuit 506 (e.g., on thesignal 505) may be to cancel and/or compensate for distortion introducedby the other elements further down the transmit path—e.g., the PGPAcircuit 508. Such distortion may dynamically change. For example,distortion introduced by the PGPA circuit 508 may change as certainconditions (e.g., temperature; power supply voltage; amplitude, phase;amplitude, phase, and/or frequency of signal 507; etc.) may change.Accordingly, in various implementations, pre-distortion may bedynamically calibrated, such as by dynamically adjusting parameters ofthe pre-distortion circuit 506 to account for such changedconditions/parameters in, or near, real-time.

For example, in the particular example implementation shown in FIG. 5,the pre-distortion control circuit 514 may be used to control or adjustthe pre-distortion being performed via the pre-distortion circuit 506,substantially as described with respect to the pre-distortion controlcircuit 114 and the pre-distortion circuit 104 of FIG. 1. In thisregard, the pre-distortion control circuit 514 may generate the controlsignal 515, which may be input to the pre-distortion circuit 506 toenable controlling and/or adjusting operations thereof. Further, asdescribed with respect to FIG. 1, the pre-distortion control circuit 514may be controlled based on input (e.g., control signal 513) from thefeedback conditioning circuit 512, thus facilitating the adaptive,feedback based, control of pre-distortion. As with the feedbackconditioning circuit 112 of FIG. 1, the feedback conditioning circuit512 may also be operable to condition one or more signals in thetransmitter, such as one or more of signals 509, 507, 505, and 503; tomake the signal(s) suitable for use by the pre-distortion circuit 514.

The result of the conditioning performed by the feedback conditioningcircuit 512 may be conveyed via the control signal 513, and ultimatelythe effect of the conditioned signals may be conveyed to (e.g., used tocontrol) pre-distortion circuit 506 via the control signal 515. As withthe pre-distortion control circuit 114 of FIG. 1, the pre-distortioncontrol circuit 514 may also be controlled based on sensory-based input,such as from the sensor 510. For example, the sensor 510 may obtaintemperature related information relating to the transmitter 500 (and/orit various components thereof), and may output based thereon the signal511, which may indicate temperature of the transmitter 500 generally,and/or of one or more of the components 502, 504, 506, 508 specifically.Other factors that may be considered in controlling the pre-distortionperformed in the transmitter 500 (e.g., being feed into and used by thepre-distortion control circuit 514) may comprise parameters relating orpertinent to function of other components (e.g., PGPA gain).

As with the transmitter 100 of FIG. 1, the feedback conditioning and/orpre-distortion control may be implemented as fully analog, fullydigital, or mixed analog-digital. Thus, similar to the feedbackconditioning circuit 112 and the pre-distortion control circuit 114 ofFIG. 1, each of the pre-distortion control circuit 514 and the feedbackconditioning circuit 512 may be implemented to (including, in someexample implementations, being dynamically configurable to variably doso) operate on digital and/or analog signals, as described in moredetail with respect to FIG. 1.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the processes as described herein.

Accordingly, various embodiments in accordance with the presentinvention may be realized in hardware, software, or a combination ofhardware and software. The present invention may be realized in acentralized fashion in at least one computing system, or in adistributed fashion where different elements are spread across severalinterconnected computing systems. Any kind of computing system or otherapparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware and software may be ageneral-purpose computing system with a program or other code that, whenbeing loaded and executed, controls the computing system such that itcarries out the methods described herein. Another typical implementationmay comprise an application specific integrated circuit or chip.

Various embodiments in accordance with the present invention may also beembedded in a computer program product, which comprises all the featuresenabling the implementation of the methods described herein, and whichwhen loaded in a computer system is able to carry out these methods.Computer program in the present context means any expression, in anylanguage, code or notation, of a set of instructions intended to cause asystem having an information processing capability to perform aparticular function either directly or after either or both of thefollowing: a) conversion to another language, code or notation; b)reproduction in a different material form.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1-20. (canceled)
 21. A system comprising: one or more circuits operableto: apply pre-distortion modification during processing of an inputsignal for transmission; generate feedback data based on a plurality offeedback signals, wherein: each of said plurality of feedback signalscorresponds to a particular processing stage performed during processingof said input signal; and generating said feedback data comprisesapplying one or more adjustments to said plurality of feedback signalsbased on a type and/or a source of at least one feedback signal, saidone or more adjustments to said plurality of feedback signals comprisingone or more of: applying a gain to one of said plurality of feedbacksignals; applying a delay to one of said plurality of feedback signals;and modifying a first one of said plurality of feedback signals based ona second one of said plurality of feedback signals; and apply one ormore adjustments to said pre-distortion modification based on saidfeedback data.
 22. The system of claim 21, wherein said one or morecircuits are operable to subtract said first one of said plurality offeedback signals from said second one of said plurality of feedbacksignals.
 23. The system of claim 21, wherein said one or more circuitsare operable to periodically determine and/or apply said one or moreadjustments to said pre-distortion modification.
 24. The system of claim21, wherein said one or more circuits are operable to determine and/orapply said one or more adjustments to said pre-distortion modificationbased on one or more parameters relating to said one or more circuits.25. The system of claim 21, wherein said one or more circuits areoperable to determine and/or apply said one or more adjustments to saidpre-distortion modification based on one or more environmentalconditions.
 26. The system of claim 25, wherein said one or morecircuits are operable to determine and/or apply said one or moreadjustments to said pre-distortion modification based on sensory datarelating to said one or more environmental conditions.
 27. The system ofclaim 21, wherein said plurality of feedback signals comprise one ormore intermediate signals generated during processing of said inputsignal after application of said pre-distortion modification.
 28. Thesystem of claim 27, wherein said one or more circuits are operable toprocess said one or more intermediate signals to generate data relatingto or derived from said one or more intermediate signals.
 29. The systemof claim 21, wherein said pre-distortion modification comprisesmodifying one or more characteristics of said input signal.
 30. Thesystem of claim 29, wherein said one or more characteristics compriseone or more of: phase, frequency, and amplitude.
 31. A methodcomprising: applying pre-distortion modification during processing of aninput signal for transmission; generating feedback data based on aplurality of feedback signals, wherein: each of said plurality offeedback signals corresponds to a particular processing stage performedduring said processing of said input signal; and generating saidfeedback data comprises applying one or more adjustments to saidplurality of feedback signals based on a type and/or a source of atleast one feedback signal, said one or more adjustments comprising oneor more of: applying a gain to one of said plurality of feedbacksignals; applying a delay to one of said plurality of feedback signals;and modifying a first one of said plurality of feedback signals based ona second one of said plurality of feedback signals; and applying one ormore adjustments to said pre-distortion modification based on saidfeedback data.
 32. The method of claim 31, wherein modifying said firstone of said plurality of feedback signals based on said second one ofsaid plurality of feedback signals comprises subtracting said first oneof said plurality of feedback signals from said second one of saidplurality of feedback signals.
 33. The method of claim 31, comprisingperiodically determining and/or applying said one or more adjustments tosaid pre-distortion modification.
 34. The method of claim 31, comprisingdetermining and/or applying said one or more adjustments to saidpre-distortion modification based on one or more parameters relating tosaid one or more circuits.
 35. The method of claim 31, comprisingdetermining and/or applying said one or more adjustments to saidpre-distortion modification based on one or more environmentalconditions.
 36. The method of claim 35, comprising determining and/orapplying said one or more adjustments to said pre-distortionmodification based on sensory data relating to said one or moreenvironmental conditions.
 37. The method of claim 31, wherein saidplurality of feedback signals comprise one or more intermediate signalsgenerated during processing of said input signal after application ofsaid pre-distortion modification.
 38. The method of claim 37, comprisingprocessing said one or more intermediate signals to generate datarelating to or derived from said one or more intermediate signals. 39.The method of claim 31, wherein said pre-distortion modificationcomprises modifying one or more characteristics of said input signal.40. The method of claim 39, wherein said one or more characteristicscomprise one or more of: phase, frequency, and amplitude.